EP0155885B1 - Dihalogen-2,3-fluor-2-propanals, process for their preparation and their application for obtaining dihalogen-2,3-fluor-2-propionic acid halides and esters, and also alkyl- or arylfluoracrylates - Google Patents

Description

The present invention relates to new dihalo-2,3-fluoro-2-propanals compounds of formula:

These compounds prove to be particularly advantageous since they allow access by synthesis to alkyl fluoroacrylates by synthesis to alkyl or aryl fluoroacrylates, which can serve as starting material for obtaining acrylic polymers having improved characteristics.

Examination of the formula of the compounds according to the invention reveals a characteristic, namely that they do not have a hydrogen atom in the alpha position with respect to the carbonyl function.

As a result, halogenation results in a substitution of the aldehyde -proton by halogen, hence the possibility of obtaining the corresponding acid halide, which in turn allows access to the acrylates.

soit de ses précurseurs et ils ont mis au point un procédé nouveau et économique à l'effet d'obtenir de bons rendements en fluoro-2-acroléine.Applicants have found that the compounds according to the invention can be obtained, inter alia, either from fluoro-2-acrolein of formula:

either of its precursors and they have developed a new and economical process for obtaining good yields of fluoro-2-acrolein.

In fact at present, only one synthesis of fluoro-2-acrolein is known. This is a laboratory synthesis. It was presented by J. Buddrus et al. - Tetrahedron Letters 1966 (44), 5379-83 and Justus Liebig - Ann. Chem., 1967, 710, 36-58.

According to these authors, a mixture of butylvinyl ether, ethylene oxide and dichlorofluoromethane is autoclaved at 150 ° C. in the presence of tetraethylammonium bromide. The reaction product is butoxy-3- (chloro-2-ethoxy) 3-fluoro-2-propene:

non isolé, lequel s'ouvrirait dans les conditions de l'essai pour donner, en réagissant avec l'oxyde d'éthylène, l'acétal II.These same authors suggest for this reaction a mechanism passing through a cyclopropane derivative of formula:

not isolated, which would open under the conditions of the test to give, on reacting with ethylene oxide, acetal II.

The hydrolysis of Il in a sulfuric medium leads to fluoro-acrolein which is isolated by distillation. The yield announced by these authors, over all of the two stages is 21.7%.

If we try to apply this synthesis on an industrial scale, the exothermicity of the reaction makes it uncontrollable when we use quantities of reagent of the order or greater than the mole; it suddenly develops pressures above 300 bars, making any extrapolation difficult.

However, the applicants overcome these drawbacks by providing a process which does not present these risks, this process being able to be carried out without the need for an autoclave by using known reactors in common use. In addition, this process does not use ethylene oxide which is still a very delicate substance to be used in large quantities.

dans laquelle R₁ et R₂ représentent des groupes alkyles identiques ou différents ayant de 1 à 8 atomes de carbone.This process consists in carrying out the hydrolysis of acetals of formula:

in which R ₁ and R ₂ represent identical or different alkyl groups having from 1 to 8 carbon atoms.

où R₁ est un alkyle de C₁ à C₈ et X est CI ou Br par solvolyse en milieu alcoolique (R₂OH) en présence d'une base, ces cycles cyclopropaniques étant eux-mêmes obtenus à partir d'un éther énolique de formule :

avec R₁ = alkyle de C₁ à C₈, par addition de halogénofluorocarbène. De façon avantageuse, on fera intervenir le chlorofluorocarbène lui-même obtenu à partir de dichlorofluorométhane (CHFCl₂) (« Fréon 21 •), en présence d'une base et d'un agent de transfert de phase.More particularly, the starting acetals are advantageously obtained by opening, under mild and controllable conditions, rings of alkoxy-1-halo-2-fluoro-2-cyclopropanes of formula:

where R ₁ is a C ₁ to C ₈ alkyl and X is CI or Br by solvolysis in an alcoholic medium (R ₂ OH) in the presence of a base, these cyclopropane rings being themselves obtained from an enolic ether of formula:

with R ₁ = C ₁ to C ₈ alkyl, by addition of halofluorocarbene. Advantageously, use will be made of the chlorofluorocarbene itself obtained from dichlorofluoromethane (CHFCl ₂ ) (“Freon 21 •), in the presence of a base and a phase transfer agent.

• a) transformation d'un alkylvinyl éther de formule :
  
  où R₁ = alkyle de C₁ à C₈, en alcoxy-2-chloro-1-fluoro-1-cyclopropane par addition de chlorofluorocarbène (CFCI). On obtient ainsi un mélange des deux isomères syn et anti de formule :

The method of implementing the method as defined above can then be diagrammed by the following series of reactions:

• a) transformation of an alkylvinyl ether of formula:
  
  where R ₁ = C ₁ to C ₈ alkyl, to alkoxy-2-chloro-1-fluoro-1-cyclopropane by addition of chlorofluorocarbene (CFCI). A mixture of the two syn and anti isomers of formula is thus obtained:

• b) conversion de l'alcoxy-2-chloro-1-fluoro-1-cyclopropane (IV) en dialcoxy-3,3-fluoro-2-propène (V) par action d'une base en milieu alcoolique suivant :
  
  avec R, et R₂ identiques ou différents = alkyle ou aryle en C₁ à C₈.

Chlorofluorocarbene is itself obtained in situ from dichlorofluoromethane (CHFCl ₂ ) ("Freon 21") in an alkaline medium (NaOH or KOH) in the presence of a phase transfer catalyst of the tetraethylammonium bromide (TEBA) type and analogues;

• b) conversion of alkoxy-2-chloro-1-fluoro-1-cyclopropane (IV) to dialkoxy-3,3-fluoro-2-propene (V) by the action of a base in the following alcoholic medium:
  
  with R, and R ₂ identical or different = C ₁ to C ₈ alkyl or aryl.

• c) hydrolyse de l'acétal (V) par un acide minéral tel que HCI ou H₂SO₄, pour obtenir, la fluoro-2-acroléine suivant :
  

Among the bases which can be used, there may be mentioned in particular pyridine, triethanolamine. soda and the like. This reaction is advantageously carried out at a temperature of the order of 110/120 ° C;

• c) hydrolysis of the acetal (V) with a mineral acid such as HCI or H ₂ SO ₄ , to obtain the following fluoro-2-acrolein:
  

The yields that can be obtained by implementing this process are of the order of 60% and more, calculated on the basis of the starting alkylvinyl ether, while in the known process, in an autoclave, the yield is only 21.7%.

avec X = CI ou Br.Having thus a means easily leading to fluoro-2-acrolein, the compounds according to the invention can be obtained directly from fluoro-2-acrolein, by addition of an equivalent of halogen (Cl ₂ or Br ₂ ). cold, depending on the reaction:

with X = CI or Br.

The dihalides can then be isolated by distillation under reduced pressure.

Or, they can be obtained from the corresponding enol ether, a raw material used for the preparation of fluoro-2-acrolein, without it being necessary to isolate said fluoroacrolein in the pure state.

The process can then be stated as follows:

At the end of this last step, the reaction medium is composed of fluoro-2-acrolein, water, and the alcohols R ₁ OH and R _z OH. Coarse drying on CaC1 ₂ followed by a simple decantation gives a mixture which can be brominated directly in the cold and which leads to dibromo-2,3-fluoro-2-propanal, which can be isolated using the techniques usual.

As indicated previously, the particularity of the 2,3-dihalo-2-fluoro-2-propanals is that one is in the presence of aldehydes having no hydrogen atoms in the alpha position relative to the carbonyl function.

Further halogenation will therefore lead to the corresponding acid halide, that is to say the 2,3-halo-2-fluoro-2-propanoyl halide. This halogenation can be done by the action of hot bromine, under ultraviolet irradiation or by the action of chlorine at room temperature.

It is thus possible to use other halogenating agents, such as N-bromo-succinimide for example. These halogenations can be carried out in the presence of free radical initiators, such as benzoyl peroxide and others.

From the abovementioned acid halide, access to alkyl or aryl fluoro-2-acrylates is relatively easy.

lequel est déshalogéné par le zinc pour finalement conduire au fluoro-2-acrylate d'alkyle ou d'aryle.The dihalogenated acid halide subjected to the action of an alcohol or a phenol in the presence of base (pyridine or triethylamine Et ₃ -N) leads to alkyl dihalo-2,3-fluoro-2-propionate or aryl.

which is dehalogenated by zinc to finally lead to alkyl or aryl fluoro-2-acrylate.

The following examples are given by way of illustration and in no way limit the present invention.

Example 1 A) Formation of butoxy-1-chloro-2-fluoro-2-cyclopropane

A solution consisting of 1.5 liters of water and 1,500 g of soda in flakes is introduced into a jacketed reactor cooled with glycol, equipped with a vigorous stirring means. This mixture being cooled to 0 ° C., 1300 ml of methylene chloride, 21.6 g of tetraethylammonium bromide and 701 g of butylvinyl ether (7 moles) are successively added.

Using a device allowing a gaseous introduction into the reaction mass, 828 g of "Freon 21 (8 moles) are injected while ensuring that the temperature does not exceed 5 ° C.

However, the end of the reaction can be ensured by the absence of vinyl protons in ¹ H NMR.

At the end of the reaction, water is added until the two phases are mixed (6.5 liters).

After decantation, the aqueous phase is extracted with methylene chloride and the organic phase is washed with a saturated solution of sodium chloride. Methylene chloride is removed. After drying by azeotropic distillation in the presence of dichloroethane, there remains a product enriched to 93% in butoxy-1-chloro-2-fluoro-2-cyclopropane.

After distillation under reduced pressure (16 mm Hg-55 ° C), 926 g of a product with 98% purity is obtained, ie a yield of 78.1% in pure product.

It is a mixture of the two syn and anti isomers.

• Eb = 55 ° C/16 mm Hg
• RMN¹H = >CH- et ―OCH₂―= motif centré à 3,68 ppm -CH₃ = motif centré à 0,96 ppm -CH₂- = motif centré à 1,49 ppm
• _RMN ¹⁹F = CDCl₃/C₆F₆ isomère syn = motif centré à 26,9 ppm isomère anti = motif centré à 5,3 ppm.

Characterization :

• Eb = 55 ° C / 16 mm Hg
• ¹ H NMR => CH- and ―OCH ₂ - = pattern centered at 3.68 ppm -CH ₃ = pattern centered at 0.96 ppm -CH ₂ - = pattern centered at 1.49 ppm
• ¹⁹ F _NMR = CDCl ₃ / C ₆ F ₆ syn isomer = motif centered at 26.9 ppm anti-isomer = motif centered at 5.3 ppm.

Tetraethylammonium bromide can be replaced by any other phase transfer agent, in particular by TEBA (triethylbenzylammonium chloride) etc.

B) Formation of ethoxy-1-chloro-2-fluoro-2-cyclopropane

A test similar to that described in A) but using ethyl vinyl ether instead of butylvinyl ether led to ethoxy-1-chloro-2-fluoro-2-cyclopropane.

• Rdt = 58 %
• Eb ₌ 112-114 °C/760 mm Hg
• RMN¹H = >CH- et -OCH₂ = motif centré à 3,75 ppm -CH₃ = motif centré à 1,27 ppm ―CH₂― = motif centré à 1,67 ppm
• _RMN ¹⁹F = CDCl₃/C₆F₆ isomère syn = motif centré à 25,5 ppm isomère anti = motif centré à 3,83 ppm

Characterization :

• Yid = 58%
• Eb ₌ 112-114 ° C / 760 mm Hg
• ¹ H NMR => CH- and -OCH ₂ = pattern centered at 3.75 ppm -CH ₃ = pattern centered at 1.27 ppm ―CH ₂ - = pattern centered at 1.67 ppm
• ¹⁹ F _NMR = CDCl ₃ / C ₆ F ₆ syn isomer = motif centered at 25.5 ppm anti isomer = motif centered at 3.83 ppm

C) Formation of isobutoxy-1-chloro-2-fluoro-2-cyclopropane.

• Caractérisation :
• Rdt = 82,1 %
• Eb = 50-55 °C/18 mm Hg
• RMN¹H = >CH- et ―OCH₂― = motif centré à 3,40 ppm ―CH₂― et >CH-(isobutyl) = motif étalé de 1,33 à 1,90 ppm ―CH₃ = doublet (0,88-0,96) ppm
• RMN¹⁹F = isomère syn à 27,1 ppm isomère anti à 5,3 ppm.

The procedure is the same using isobutylvinylether.

• Characterization :
• Yid = 82.1%
• Eb = 50-55 ° C / 18 mm Hg
• ¹ H NMR => CH- and ―OCH ₂ - = centered pattern at 3.40 ppm ―CH ₂ - and> CH- (isobutyl) = spread pattern from 1.33 to 1.90 ppm ―CH ₃ = doublet (0 , 88-0.96) ppm
• ¹⁹ F NMR = syn isomer at 27.1 ppm anti isomer at 5.3 ppm.

Example 2 A) Formation of di-n-butoxy-1,1-fluoro-2-propene

102.5 g of nBuOH and 43.4 g of pyridine are introduced into a three-necked flask fitted with a dropping funnel and a reflux device.

The mixture is brought to reflux, then 83 g of butoxy-1-chloro-2-fluoro-2-cyclopropane are poured in, as prepared in 1A. The reflux is maintained for two and a half to three hours. After cooling, approximately 90 ml of water are introduced until the pyridine hydrochloride dissolves.

After treatment of the reaction medium (decantation, washing and extraction of the different phases, evaporation of the solvents), the acetal is distilled.

• Caractérisation :
• _Eb = ₆₄-_{67 °C/4} mm _Hg
• RMN¹H = ―CH₂― et >CH- = motif centré à 4,77 ppm OCH₂― = motif centré à 3,57 ppm ―CH₂― = motif centré à 1,52 ppm CH₃- = motif centré à 0,92 ppm
• RMN¹⁹F = CDCl₃/C₆F₆ = motif centré à 52,3 ppm.

81.6 g of an acetal with 98% purity are collected, ie a yield of 78.4% in pure product.

• Characterization :
• _Eb = ₆₄ - _{67 ° C / 4} mm _H g
• ¹ H NMR = ―CH ₂ - and> CH- = motif centered at 4.77 ppm OCH ₂ - = motif centered at 3.57 ppm ―CH ₂ - = motif centered at 1.52 ppm CH ₃ - = motif centered at 0.92 ppm
• NMR ¹⁹ F = CDCl ₃ / C ₆ F ₆ = motif centered at 52.3 ppm.

B) Formation of di-isobutoxy-1,1-fluoro-2-propene

The procedure is as described in A) above but using isobutoxy-1-chloro-2-fluoro-2-cyclopropane and isobutanol.

• Rdt = 77,2 %
• Eb = 73-76 °C/4 mm Hg
• RMN¹H = ―CH₃ = doublet 0,89 à 0,97 ppm ―CH<(iBu) = multiplet centré à 1,87 ppm OCH₂― = motif centré à 3,30 ppm >CH_z- et ―CH<(cycle) = motif allant de 4,50 à 5,11 ppm.

Di-isobutoxy-1,1-fluoro-2-propene is thus obtained, characterized by:

• Yid = 77.2%
• Eb = 73-76 ° C / 4 mm Hg
• ¹ H NMR = ―CH ₃ = doublet 0.89 to 0.97 ppm ―CH <(iBu) = multiplet centered at 1.87 ppm OCH ₂ - = pattern centered at 3.30 ppm> CH _z - and ―CH < (cycle) = pattern ranging from 4.50 to 5.11 ppm.

C) A test identical to that described in A) above was carried out by replacing the pyridine with triethanolamine.

The evolution is much slower. After 5 hours, a C.P.G. reveals that 20% of the starting material has not yet reacted. It is necessary to maintain the reflux for about fifteen hours so that the whole of the cyclopropane derivative disappears.

After treatment, the acetal could be isolated with a yield of the order of 50%.

Example 3 A) Formation of fluoroacrolein

408 g of di-n-butoxy-1,1-fluoro-2-propene (2 moles) and 750 ml of liquid are placed in a 2-liter reactor equipped with a distillation head with total reflux and a condenser. hydrochloric acid N.

The reflux head being closed, it is brought to reflux. The vapor temperature on the distillation head which is approximately 93 ° C (azeotrope butanol-water) slowly drops to stabilize around 77-78 ° C, after about an hour. At this instant, the distillate is recovered in the recipe until the temperature stabilizes again around 93 ° C. About 340 g of a ternary mixture are thus collected: fluoro-2-acrolein, water and butanol.

The mixture is put on calcium chloride; it is left to settle and then distilled "bulb to bulb". This sequence of operations is repeated two to three times consecutively, depending on the purity of the product desired.

• Caractérisation :
• RMN¹H = dans CDCl₃ proton aldéhyde : 2 pics à 9,26-9,48 ppm proton vinylique : motif centré à 5,65 ppm
• RMN¹⁹F = CDCl₃/C₆F₆ : motif centré à 41,8 ppm.

123.4 g of a product with 97.6% purity (CPG) are thus isolated, ie a yield of 81.4% in pure product.

• Characterization :
• ¹ H NMR = in CDCl ₃ aldehyde proton: 2 peaks at 9.26-9.48 ppm vinyl proton: centered motif at 5.65 ppm
• ¹⁹ F NMR = CDCl ₃ / C ₆ F ₆ : motif centered at 41.8 ppm.

Example 4 Formation of dibromo-2,3-fluoro-2-propanal from fluoroacroline

111 g of fluoro-2-acrolein (1.5 mole) dissolved in 110 ml of carbon tetrachloride are introduced into a 500 ml flask fitted with a magnetic stirrer, condenser and dropping funnel. While maintaining the temperature at around 0 ° C., 240 g of bromine (1.5 mol) are poured slowly. After discoloration of the medium and evaporation of the carbon tetrachloride, chromatography in aqueous phase reveals that there is a relatively pure product (95%).

• m = 182 g, soit un rendement de l'ordre de 52 %.

This product can be distilled under reduced pressure. We thus obtain:

• m = 182 g, i.e. a yield of the order of 52%.

• Eb = 56-57 °C sous 19 mm Hg
• RMN¹H = proton aldéhyde = motif centré à 9,31 ppm ―CH₂― = motif centré à 4,13 ppm
• RMN¹⁹F = CDCl₃/C₆F₆ = motif centré à 34,30 ppm

Characterization :

• Bp = 56-57 ° C under 19 mm Hg
• ¹ H NMR = proton aldehyde = motif centered at 9.31 ppm ―CH ₂ - = motif centered at 4.13 ppm
• NMR ¹⁹ F = CDCl ₃ / C ₆ F ₆ = motif centered at 34.30 ppm

Example 5 Formation of dichloro-2,3-fluoro-2-propanal from fluoroacrolein

• Caractérisation :
• Eb = 110-113 °C/760 mm Hg
• RMN¹H = CH₂ = 4,03 et 4,3 ppm CH- = 9,55 ppm
• RMN¹⁹F = CDCl₃/C₆F₆ : motif à 31 ppm.

The procedure is as in Example 4, cold (―10 ° C to ―15 ° C), in the presence of chlorine.

• Characterization :
• Eb = 110-113 ° C / 760 mm Hg
• ¹ H NMR = CH ₂ = 4.03 and 4.3 ppm CH- = 9.55 ppm
• ¹⁹ F NMR = CDCl ₃ / C ₆ F ₆ : motif at 31 ppm.

Example 6 Formation of dibromo-2,3-fluoro-2-propanoyl bromide A) From dibromo-2,3-fluoro-2-propanal

To 0.05 mole of dibromo-2.3-fluoro-2-propanal dissolved in 37 ml of CC1 ₄ , 80 g of bromine and 0.2 g of benzoyl peroxide are added quickly and cold. It is then brought to reflux at the same time as it is irradiated under ultraviolet light. Periodic samples subjected to the CPG make it possible to follow the evolution of the reaction which is stopped after disappearance of the starting product.

After evaporation of the excess bromine and the solvents, there is a relatively pure product which can be used as it is.

Distillation under reduced pressure allows additional purification: m = 117.3 g, purity more or less 90%, or a yield of pure product of the order of 67.5%.

• Eb = 54 °C/6 mm Hg
• RMN¹H = motif centré à 4,30 ppm (4 pics : 4,52-4,38 4,21-4,07 ppm)
• RMN¹⁹F = CDCl₃/C₆F₆ : motif centré à 54,57 ppm.

Characterization :

• Eb = 54 ° C / 6 mm Hg
• ¹ H NMR = motif centered at 4.30 ppm (4 peaks: 4.52-4.38 4.21-4.07 ppm)
• ¹⁹ F NMR = CDCl ₃ / C ₆ F ₆ : motif centered at 54.57 ppm.

B) From fluoroacrolein

37 g of fluoro-2-acrolein (0.5 mole) dissolved in 37 ml of CCl ₄ are introduced into a 250 ml flask fitted with a stirrer, a condenser and a dropping funnel. While the mixture is cooled to -5 ° C, 0 ° C, 79 g of bromine is poured slowly, via the dropping funnel. We observe discoloration as and when added.

At the end of the addition, still cold, 80 g of bromine are quickly poured into the mixture, then the mixture is brought to reflux at the same time as it is irradiated under ultraviolet light.

After three hours of reflux, it is verified that all of the fluoroacolein has been consumed. Distillation under reduced pressure (6 mm-54 ° C) makes it possible to isolate 116.7 g of acid bromide with 89% purity, ie a yield of pure product of 66.6%.

Example 7 Formation of dichloro-2,3-fluoro-2-propanoyl chloride

A stream of chlorine is bubbled through a solution consisting of 2.9 g of 2,3-dichloro-2,3-fluoro-2-propanal dissolved in methylene chloride, at a temperature of -15 ° C, -10 ° C.

The bubbling is stopped when a sample subjected to a ¹⁹ F NMR spectrum shows the disappearance of the line corresponding to the aldehyde (31 ppm).

• Caractérisation :
• Eb = 100-108 °C/760 mm
• RMN¹H = motif de 4,1 à 4,7 ppm
• RMN¹⁹F = motif à 47 ppm
• Rdt = 30 %

After evaporation of the solvents and distillation, the dichloro-2,3-fluoro-2-propanoyl chloride is obtained:

• Characterization :
• Eb = 100-108 ° C / 760 mm
• ¹ H NMR = motif from 4.1 to 4.7 ppm
• ¹⁹ F NMR = motif at 47 ppm
• Yid = 30%

Example 8 Formation of phenyl-2,3-fluoro-2-propionate A) From potassium phenate

150 g of dibromo-2,3-fluoro-2-propanoyl bromide (69% content, or 0.33 mole) are introduced into a one liter reactor, under an argon atmosphere, with stirring and refrigerant. ml of CH ₂ Cl ₂ . The mixture being maintained at 0 ° C., 63 g of freshly prepared potassium phenate are added. After stirring for one hour at 0 ° C., the mixture is allowed to return to ambient temperature.

After adding 120 ml of water and decanting, the aqueous phase is extracted with methylene chloride.

All of the organic phases are washed with a water-sodium hydrogen carbonate mixture and then distilled.

The 105-115 ° C / 0.7 mm Hg fraction makes it possible to isolate 85.7 g of phenyl dibromo-2,3-fluoro-2-propionate, ie a yield of the order of 79.6%.

• Eb = 105-115 °C/0,7 mm Hg
• RMN¹H = ―CH₂―= motif centré de 4,09 à 4,56 ppm phényl = motif centré à 7,3 ppm
• RM_N ¹⁹F = motif centré à 43,63 ppm.

Characterization :

• Eb = 105-115 ° C / 0.7 mm Hg
• ¹ H NMR = ―CH ₂ - = centered motif from 4.09 to 4.56 ppm phenyl = centered motif at 7.3 ppm
• RM _N ¹⁹ F = pattern centered at 43.63 ppm.

B) From phenol in the presence of pyridine

66.7 g of phenol (0.75 mole) dissolved in 750 ml of carbon tetrachloride are introduced into a 2-liter flask fitted with a stirrer, a condenser and a dropping funnel. A further 59.2 g of pyridine (0.75 mole) are added using the dropping funnel.

The whole being maintained on a cooling bath so that the temperature does not exceed 20 ° C., the crude acid bromide (dibromo-2,3-fluoro-2-propanoyl bromide) resulting from the bromination of 0 is added. , 75 mole of fluoro-2-acrolein, and this slowly, via the dropping funnel. A white precipitate of pyridine hydrobromide is formed.

After having left under stirring for approximately one hour, the sufficient quantity of water necessary for the dissolution of the precipitate of pyridine hydrobromide is added. After treatment of the reaction medium (decantation, extraction, etc.) and distillation under reduced pressure, 191.0 g (105 ° C. / 0.5 mm Hg) of a product of 97% purity are collected, ie a yield of pure product 75.7% (calculated over the two stages, from fluoro-2-acrolein).

Example 9 Formation of methyl dibromo-2,3-fluoro-2-propionate

The procedure is identical to that described in 8B), replacing the phenol with methanol. Methyl dibromo-2,3-fluoro-2-propionate was thus obtained with a yield of the order of 70% calculated over the two stages, starting from the fluoro-2acrolein used.

• Eb = ₅₈-_{60 °C/1},₅ mm Hg
• RMN¹H = - OCH₃ = motif centré à 3,93 ppm ― CH₂ ― = motif à 4 pics étalés de 4,49 à 4,04 ppm
• RMN¹⁹F = CDCl₃/C₆F₆ = motif centré à 4,39 ppm.

Characterization :

• Bp = _{58-60 ° C / 1 5} mm Hg
• ¹ H NMR = - OCH ₃ = motif centered at 3.93 ppm - CH ₂ - = motif with 4 peaks spread from 4.49 to 4.04 ppm
• ¹⁹ F NMR = CDCl ₃ / C ₆ F ₆ = centered motif at 4.39 ppm.

Example 10 Isopropyl dibromo-2,3-fluoro-2-propionate formation

The operation is carried out in a 4-liter reactor fitted with a mechanical stirrer, a dropping funnel and a refrigerant. 3690 g of CCl ₄ and 165 g (2.75 moles) of isopropyl alcohol are introduced. Maintained at a temperature between ―5 5 and 0 ° C and poured 227.8 g of pyridine (2.88 moles).

Then dibromo-2,3-fluoro-2-propanoyl bromide, or 1,172.6 g of crude acid bromide, corresponding to the bromination of 2.75 moles of fluoro-2-acrolein, is added.

There is formation of a hydrobromide precipitate. The stirring is left for approximately 24 hours until the analysis shows the disappearance of the acid bromide.

170 ml of water are added. After decantation, washing of the organic phase twice with 150 ml H ₂ 0, extraction of the aqueous phases with CCI ₄ , evaporation of the solvents, and collection is carried out by distillation under reduced pressure (58 ° C. under 1 mm Hg): 663 g dibromo ester, purity 97.1%, ie a yield of pure product of 80.2%.

Example 11 Formation of phenyl fluoro-2-acrylate

110 g of phenyl dibromo-2,3-fluoro-2-propanolate (i.e. 0.337 mole) in solution in a one liter flask inerted with argon, with stirring and a condenser 350 ml of isopropyl ether, then 65 g of zinc powder.

The whole is maintained at reflux for 4 hours. After returning to ambient temperature, the reaction medium is filtered. After removal of the solvents, bulb-to-bulb distillation makes it possible to collect 44 g of phenyl fluoro-2-acrylate (0.264 mole), ie a yield of the order of 78.6%.

• Eb = 52-54 °C/0,5 mm Hg
• RMN¹H = protons vinyliques : motif centré de 5,31 à 6,11 ppm -phényl : motif centré à 7,27 ppm
• RMN¹⁹F = CDCl₃/C₆F₆ : motif centré à 47,65 ppm.

Characterization :

• Eb = 52-54 ° C / 0.5 mm Hg
• ¹ H NMR = vinyl protons: centered motif from 5.31 to 6.11 ppm -phenyl: centered motif at 7.27 ppm
• ¹⁹ F NMR = CDCl ₃ / C ₆ F ₆ : motif centered at 47.65 ppm.

Example 12 Isopropyl fluoro-2-acrylate formation

2 liters of isopropyl ether, 160 g of powdered zinc (2.44 moles) and a spike are introduced into a 4-liter reactor fitted with a mechanical stirrer, a condenser and a dropping funnel. hydroquinone spatula.

The whole is brought to reflux while 586 g of dibromo-ester at 97%, or 1.95 mole, are poured in.

After cooling, filtration, washing the precipitate with isopropyl ether, washing the organic phase with water to remove the zinc salts, 220.7 g of isopropyl fluoroacrylate at 99.4% purity are collected by distillation. , or a yield of the order of 85%.

It goes without saying that the present invention has been described for purely explanatory and in no way limitative and that any useful modification may be made without departing from its scope.

Claims (13)

1. Novel industrial products complying with the formula :

in which X =Cl or Br.

2. A process for preparing products according to Claim 1, characterized in that it consists of halogenating 2-fluoroacrolein by direct addition of halogen X₂.

3. A process according to Claim 2, characterized in that the said 2-fluoroacrolein is obtained by hydrolysis of acetals having the formula :

in which R₁ and R₂ represent identical or different alkyl groups having 1 to 8 carbon atoms, the acetals being obtained by opening under mild and controllable conditions the rings of 1-alkoxy-2-halogen-2-fluorocyclopropanes having the formula :

where R_j is a C₁ to C₈ alkyl group and X is chlorine or bromine, this opening being performed by solvolysis in an alcoholic medium employing alcohols R₂OH, where R₂ is a C, to C₈ alkyl group, in the presence of a base.

4. A process according to Claim 3, characterized in that the base is chosen from pyridine, triethanolamine or soda.

5. A process according to Claim 3, characterized in that the 1-alkoxy-2-halogen-2-fluoro-cyclopropane is obtained from an ether of an enol having the formula :

where R₁ = C₁ to C₈ alkyl.

6. A process according to Claim 5, characterized in that a halogenfluorocarbene, and more especially chlorofluorocarbene : CFCI, is added to the said enol ether.

7. A process according to Claim 6, characterized in that the said chlorofluorocarbene is prepared in situ from CHFCl₂ (« Freon 21 •) in the presence of a base and a phase transfer agent.

8. A process according to Claim 7; characterized in that the said base is NaOH or KOH.

9. A process according to Claim 7, characterized in that the said phase transfer agent is triethylbenzylammonium chloride or tetraethylammonium bromide.

10. Products complying with the formula :

in which X = CI or Br, suitable for employment in a process for manufacturing an alkyl or aryl fluoracrylate having the formula :

in which Z is an alkyl or aryl group, comprising the stage of preparing a halide of 2,3-dihalogen-2-fluoropropionic acid having the formula :

in which X and Y are CI or Br, identical or different, by halogenation of the said products according to Claim 1 using an agent chosen from chlorine, bromine and N-bromo-succinimide, followed by the stage of preparing an ester having the formula :

where Z has the meaning given above, followed by a dehalogenation stage to obtain the said alkyl or aryl fluoracrylate.

11. A product complying with the formula :

in which X = Br, suitable for employment in a process for manufacturing an alkyl or aryl fluoracrylate having the formula :

in which Z is an alkyl or aryl group according to Claim 10, in which the said halide of 2,3-dihalogen-2-fluoropropionic acid is the new compound having the formula :

12. Products complying with the formula :

in which X = CI or Br, suitable to be employed in a process according to Claim 10, in which their halogenation is performed by bromine using ultraviolet radiation.

13. Products complying with the formula :

in which X = C_l or Br, suitable to be employed in a process according to Claim 10, in which their halogenation by N-bromo-succinimide is performed in the presence of initiators of free radicals.